The distance between two consecutive trains is set to guarantee that the rear will not hit the front even if the front stops abnormally and abruptly. Some track joints, as shown in FIG. 1A, do not need to change the track connection when two trains on different tracks get on the same track, Others, as shown in FIGS. 1B and 1C, do. Each bifurcation needs to change the track connection when two trains on the same track get on different tracks. If a two way railroad has two way branches, it is difficult to avoid railroad intersections that may or may need to change the track connection. For those cases that, after a train passes, the track connection needs to be changed for the next train to pass, the distance between two consecutive trains is set to guarantee that the track connection is changed correctly before the rear passes the joint, the bifurcation, or the intersection, respectively. If the track cannot change the connection correctly in time, the train can stop before the joint, the bifurcation, or the intersection, respectively. Since there are not good means to determine how long the distance between two consecutive trains is enough, the distance is usually set to be much longer than enough. This limits the capacity of the railroad.